This is a video of our completed model with hydraulic actuation. The hydraulic system includes a brushless motor with a pump mounted to it, a reservoir, hydraulic oil, an electronic speed controller, hydraulic hosing, 3 double-acting hydraulic cylinders, 3 servos, a valve block (controlled by the three servos), and a battery. Below is an image that shows the basis of hydraulic circuit. The fluid is pumped from the reservoir to the first valve then to the second valve and finally the third valve. After exiting the third valve, the fluid is pumped back into the reservoir. These valves have three positions: left, right, and neutral. Depending on the orientation of the valve block, the left position makes the cylinder either extend or retract. The right position makes the cylinder move in the direction opposite that of the left position. The neutral position is considered bypass mode resulting in the cylinder not moving and the fluid going straight back to the reservoir.
We chose to go with a hydraulic system because it allows for a delivery of a lot of power in a fairly small package. The foot was moved in a variety of configurations so that it is easily understandable what the ambulation and range of motion of our device is.